The receptor for tissue plasminogen activator (t‐PA) in complex with its inhibitor, PAI‐1, on human hepatocytes

Abstract

The binding of t‐PA‐PAI‐1 to human hepatocytes at 4°C reached a maximum at 2 h. Scatchard analysis indicated 74000 ± 11000 high‐affinity binding sites for complex per human hepatocyte, with aK ₄ of 0.87 ± 0.09 mM. Almost identical results were achieved with the human hepatoma cell line Hep G2. Binding of [¹²³I]t‐PA‐PAI‐1 complex was unaffected by high concentrations of unlabelled t‐PA, PAI‐1, u‐PA or u‐PA‐PAI‐1 complex; only t‐PA‐PAI‐1 complex competed for binding. Hepatocyte‐bound t‐PA‐PAI‐1 was internalized and degraded at 37°C. Thus, hepatocytes have a specific t‐PA‐PAI‐1 receptor that participates in clearance of this complex.